The present invention relates to a device for activating the shutter blades of a motor-driven shutter in a camera.
A device for activating shutter blades by the use of a motor instead of springs, as is conventional, is installed in a camera equipped with a lens shutter which can vary the focal distance of the lens. Since such a device greatly simplifies the mechanism that interconnects the lens and the body of the camera, it is frequently used. The structure of such devices is known and disclosed in Japanese Laid-Open Patent Publication Nos. 150829/1982 and 57327/1985.
In the structure disclosed in these Japanese patent publications, shutter blades make rectilinear sliding motion and, therefore, at least two support portions are needed to limit the rectilinear sliding motion of the shutter blades. Since a large frictional resistance is produced, the blades are unable to respond quickly to the rotation of the motor. Hence, it is difficult to accurately control the operation of the shutter blades.
In the structure disclosed in the latter Japanese patent publication, shutter blades are driven near their axes of rotation so that there is a high efficiency of operation. However, rattle produced because of the clearances between the components is augmented by the portions of the shutter blades which control the exposure. The shutter blades cannot quickly respond to the rotation of the motor because of the augmented rattle and the moment of inertia in the same way as the aforementioned structure. Consequently, it is difficult to accurately control the operation of the shutter blades.
Especially where shutter blades acting also as a diaphragm are driven by a motor and when subjects are bright, exposure errors are greatly augmented. Special provisions are needed for cameras using a photosensitive material having a narrow latitude. In the structure disclosed in the previously-mentioned Japanese patent publication, the shutter blades effect rectilinear sliding movement such that each component must be disposed nonuniformly around the shutter opening. As a result, the arrangement of the lens of the camera is unusual and singular.